1. In the name of ALLAH who is most
merciful and beneficent

2. Physiology
• Membrane physiology nerve and muscle
By:
Dr. Rikza Naseer

3. The Neuromuscular
Junction
• Each nerve ending makes a junction, called the
neuromuscular junction, with the muscle fiber
near its midpoint.

4. Cont…
• The nerve fiber forms a complex of branching
nerve terminals that invaginate into the surface
of the muscle fiber but lie outside the muscle
fiber plasma membrane. The entire structure is
called the motor end plate.

5. cont…
• synaptic cleft
The space between the terminal and the
fiber membrane is called the synaptic space or
synaptic cleft.
• sub neural clefts
At the bottom of the gutter are numerous
smaller folds of the muscle membrane called sub
neural clefts.

6. Cont…

7. Cont…
• In the axon terminal are many mitochondria
that supply adenosine triphosphate (ATP), the
energy source that is used for synthesis of an
excitatory transmitter acetylcholine.
• In the synaptic space are large quantities of the
enzyme acetyl cholinesterase, which destroys
acetylcholine

8. Safety Factor:
• The term 'safety factor' refers to the ability of
neuromuscular transmission to remain effective under
various physiological conditions and stresses.
• This is a result of the amount of
transmitter released per nerve impulse
being greater than that required to trigger
an action potential in the muscle fibre.
The safety factor is a measure of this
excess of released transmitter.

9. Molecular Biology of Acetylcholine
Formation
and Release
• Acetylcholine is synthesized in the cytosol of the
nerve fiber terminal but is immediately
transported through the membranes of the
vesicles to their interior.
• Action potential
• Calcium gated channels open
• Acetylcholine in synaptic spaces
• Acetyl cholinestrases

10. Drugs That Stimulate the Muscle Fiber by
Acetylcholine-Like Action.
• Methacholine
• carbachol
• Nicotine

11. Drugs That Stimulate the Neuromuscular
Junction by Inactivating
Acetylcholinesterase
• Neostigmine
• Physostigmine
• Diisopropyl fluorophosphates

12. Drugs That Block Transmission at the
Neuromuscular Junction
• D-tubocurarine

13. Myasthenia Gravis:
• is an autoimmune
• muscle paralysis because of inability of the
neuromuscular junctions to transmit enough
signals from the nerve fibers to the muscle
fibers.
• The disease usually can be ameliorated for
several hours by administering neostigmine or
some other anticholinesterase drug

14. Excitation-Contraction
Coupling
• By t-tubules
• Deep muscle contraction

15. •